Dermatitis herpetiformis this is characterised by

Dermatitis herpetiformis
This is characterised by crops of intensely itchy blisters over the elbows,
knees, back and buttocks.
Immunofluorescence shows granular or linear IgA deposition at the
dermo-epidermal junction.
Almost all patients have partial villous atrophy on jejunal biopsy, even
though they usually have no gastrointestinal symptoms.
In contrast, fewer than 10% of coeliac patients have evidence of
dermatitis herpetiformis, although both disorders are associated with
the same histocompatibility antigen groups.
The rash usually responds to a gluten-free diet but some patients
require additional treatment with dapsone (100–150 mg daily).

Tropical sprue
Tropical sprue is defined as chronic, progressive malabsorption
in a patient in or from the tropics, associated with abnormalities of
small intestinal structure and function.
The disease occurs mainly in the West Indies and in Asia, including
southern India, Malaysia and Indonesia.
Pathophysiology
The epidemiological pattern and occasional epidemics suggest that an
infective agent may be involved.
Although no single bacterium has been isolated, the condition often
begins after an acute diarrhoeal illness.
Small bowel bacterial overgrowth with Escherichia coli,Enterobacter and
Klebsiella is frequently seen.
The changes closely resemble those of coeliac disease.

Clinical features
There is diarrhoea, abdominal distension, anorexia, fatigue and
weight loss.
In visitors to the tropics the onset of severe diarrhoea may be
sudden and accompanied by fever.
When the disorder becomes chronic, the features of
megaloblastic anaemia (folic acid malabsorption) and other
deficiencies, including ankle oedema, glossitis and stomatitis,
are common.
Remissions and relapses may occur.
The differential diagnosis in the indigenous tropical population
is an infective cause of diarrhoea.
The important differential diagnosis in visitors to the tropics is
giardiasis.

Management
Tetracycline 250 mg 6-hourly for 28 days is the treatment of choice and
brings about long-term remission or cure.
In most patients pharmacological doses of folic acid (5 mg daily)
improve symptoms and jejunal morphology.
In some cases treatment must be prolonged before improvement
occurs, and occasionally the patient must leave the tropics.

Small bowel bacterial overgrowth (‘blind loop syndrome’)
The normal duodenum and jejunum contain less than 104/mL
organisms which are usually derived from saliva.
The count of coliform organisms never exceeds 103/mL.
In bacterial overgrowth there may be 108–1010/mL organisms, most of
which are normally found only in the colon.
Disorders which impair the normal physiological mechanisms controlling
bacterial proliferation in the intestine predispose to bacterial
overgrowth .
The most important are loss of gastric acidity, impaired intestinal
motility and structural abnormalities which allow colonic bacteria to
gain access to the small intestine or provide a secluded haven from the
peristaltic stream.